feat: add Bun v1.2.15 to dogfood image (#18154)

## Summary
- Adds Bun JavaScript runtime (v1.2.15) to the dogfood image
- Installs Bun to /usr/local/bin to ensure persistence when /home/coder
is mounted
- Verified that Bun works correctly in the built container

## Test plan
1. Build the dogfood image with `cd dogfood/coder && docker build -t
codercom/oss-dogfood:test .`
2. Run the container with `docker run --rm -it codercom/oss-dogfood:test
bash`
3. Test Bun in the container with:
   - `bun --version` (should output 1.2.15)
- `cd /tmp && echo "console.log('Hello from Bun\!');" > test.js && bun
run test.js`

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

dogfood/coder/Dockerfile

@@ -287,7 +287,8 @@ ARG CLOUD_SQL_PROXY_VERSION=2.2.0 \
 	TERRAGRUNT_VERSION=0.45.11 \
 	TRIVY_VERSION=0.41.0 \
 	SYFT_VERSION=1.20.0 \
-	COSIGN_VERSION=2.4.3
+	COSIGN_VERSION=2.4.3 \
+	BUN_VERSION=1.2.15
 
 # cloud_sql_proxy, for connecting to cloudsql instances
 # the upstream go.mod prevents this from being installed with go install
@@ -331,7 +332,13 @@ RUN curl --silent --show-error --location --output /usr/local/bin/cloud_sql_prox
 	tar --extract --gzip --directory=/usr/local/bin --file=- syft && \
 	# Sigstore Cosign for artifact signing and attestation
 	curl --silent --show-error --location --output /usr/local/bin/cosign "https://github.com/sigstore/cosign/releases/download/v${COSIGN_VERSION}/cosign-linux-amd64" && \
-	chmod a=rx /usr/local/bin/cosign
+	chmod a=rx /usr/local/bin/cosign && \
+	# Install Bun JavaScript runtime to /usr/local/bin
+	curl --silent --show-error --location --fail "https://github.com/oven-sh/bun/releases/download/bun-v${BUN_VERSION}/bun-linux-x64.zip" --output /tmp/bun.zip && \
+	unzip -q /tmp/bun.zip -d /tmp && \
+	mv /tmp/bun-linux-x64/bun /usr/local/bin/ && \
+	chmod a=rx /usr/local/bin/bun && \
+	rm -rf /tmp/bun.zip /tmp/bun-linux-x64
 
 # We use yq during "make deploy" to manually substitute out fields in
 # our helm values.yaml file. See https://github.com/helm/helm/issues/3141